C Language Basics for Beginners

C programming is an excellent language to learn to program for beginners. Our C tutorials will guide you to learn C programming one step at a time.

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C# Basics for Beginners

Intro

C# vs .NET

is a programming Lang

.NET

framework for building applications on Windows

also support diff lang

VB.NET

.NET

consists of

CLR (Common Language Runtime)

translate IL(Intermediate Language) into Native Code

JIT (Just In Time Compilation)

Class Library

for building applications

Classes collaborate with each other at runtime

Architecture of .NET Applications

Application

consists of building blocks called Classes

Class

Attributes

state of application

Functions/Methods

behavior

execute code

Namespace

way to organize Classes

container for related classes

Assembly

way of partitioning an application

container for related namespaces/classes

File on disk

DLL

Dynamically Link Library

a file that includes code that can be re-used across different programs

EXE

a program that can be executed

When application is complied

compiler builds 1 or more assemblies(depending on how code is partition)

Visual Studio

Run

Ctrl + F5

Delete line

Ctrl + X

ReSharper

Alt + Enter

Get rid of unused "using" namespaces

Console.WriteLine()

Compile

Ctrl + Shift + B

3. Primitive Types & Expressions

14. Variables & Constants

Variable

Name given to a storage location in memory

Use Camel Case

Eg.

firstName

Constant

Immutable value

const float Pi = 3.14f;

Use Pascal Case

Eg.

MaxZoom

Primitive Types

byte

int

long

decimal

char

bool

15. Overflowing

"checked" keyword

Use

checked { byte number = 255; number = number +1; // 0}

will throw exception if run

without "checked", it'll overflow without error returning "0"

16. Scope

17. Demo

Default number with decimal

double

need to append 'f' behind the decimal number

Eg.

float total = 123.12f

Keywords are in blue

Code snippet

Shortcut for "Console.WriteLine()"

type "cw", double Tab

"var" keyword

Object Browser

"Ctrl + click" on keywords

doesn't work! -RL

Place-holder

Eg.

Console.WriteLine("{0} {1}", byte.MinValue, byte.MaxValue);

{0}

1st place-holder format

18. Type Conversion

Implicit Type Conversion

No data lose

Eg.

byte b = 1;int i = b;

int i = 1;float f = i;

Explicit Type Conversion(Casting)

Data will be lost if the "type" is beyond the capacity

Eg.

w/o Casting

CANNOT Compile

int i = 1;byte b = i;

w/ Casting

CAN Compile

int i = 1;byte b = (byte)i;

float f = 1.0f;int i = (int)f;

Conversion between Non-compatible types

use

Convert class

Eg.

string s = "3";int i = Convert.ToInt32(s);

ToByte()

ToInt16()

short

ToInt32()

int

ToInt64()

long

Parse method

Eg.

string s = "3";int j = int.Parse(s);

19. Demo - Type Conversion

Exception handling

try/catch

try {} catch (Exception) {}

20. Operators

Arithmetic

Add

Subtract

Multiple

Divide

Remainder

Increment

Decrement

Prefix

Eg.

int a = 1;int b = ++a; // a = 2, b = 2

Postfix

Eg.

int a = 1;int b = a++; // a = 2, b = 1

Comparison

Equal

Not Equal

Greater than

Greater than or equal to

Less than

Less than or equal to

Assignment

Addition

Subtraction

Multiplication

Division

Logical

And

Not

Bitwise

for low level Programming

And

21. What are Logical Operators?

ONLY if both are true, it's true

If ANY of the both is true, it's true

23. Demo - Operators

if division of 2 int, return will be int as well

Eg.

var a = 10;var b = 3;Console.WriteLine(a / b); // return 3

var a = 10;var b = 3;Console.WriteLine((float)a / (float)b); // return 3.333333

changing precedence

use

parenthesis

()

24.

Comments

Single-line

// This is a comment.

Multi-line

/* This is a comment.This is a comment too.*/

4. Non-primitive Types

26. Classes

Variables(Fields)

functions(Methods)

Object

instance of a Class

Declaring

Access modifier

Eg.

public

"class" keyword

identifier

Eg.

Person

Eg.

public class Person{ public string Name; public void Introduce() { Console.WriteLine("Hi, my name is " + Name); }}

Creating Objects

Eg.

var person = new Person();person.Name = "Richard";person.Introduce();

Static Modifier

can directly access the method through the Class itself, w/o creating an Object

Eg.

public class Calculator{ public static int Add(int x, int y) { return x + y; }} int result = Calculator.Add(1, 2);

27. Demo - Classes

Move class to a file

select the class

Press - Alt + Enter

Press Ctrl + "."

Switch between different Windows

Ctrl + tab

28. Structs

similar to Classes

Eg.

public struct RgbColor{ public int Red; public int Green; public int Blue;}

not frequently used

use if you want to define a small lightweight object, or else just stick to Classes

more efficient to define as struct if need to define lots of it

29. Arrays

What is?

Data structure to store a collection of variables of the same type

Declaring

Eg.

int[] numbers = new int[3];

int[]

declaring array

int[3]

set size of array

var numbers = new int[3];

Initializing

Eg.

int[] numbers = new int[3] {1, 2, 3};

Access Array Elements

Eg.

numbers[1] = 3;

30. Demo - Arrays

31. Strings

What is?

sequence of characters

Eg.

"Hello World"

How to create?

Using

Literals

Eg.

string firstName = "Richard";

Concatenation

Eg.

string name = firstName + " " + lastName;

Format

Eg.

string name = string.Format("{0} {1}", firstName, lastName);

{0}

Place holder

Join

Eg.

var numbers = new int[3] {1, 2, 3};string list = string.Join(",", numbers); // return 1,2,3

String Elements

Eg.

string name = "Richard";char firstChar = name[0]; // return 'R'

Strings are Immutable

Once Created, CANNOT change!

name[0] = 'r';

Escape Characters

Use

New Line

Tab

Backslash

Single Quotation Mark

Double Quotation Mark

Eg.

string path = "c:\\projects\\project1\\folders";

Verbatim Strings

Use

Eg.

string path = @"c:\projects\project1\folders";

32. Demo - Strings

.NET

string

map to

String

class

int

map to

Int32

struct

Eg.

String firstName = "Richard";

Can also use "String" keyword instead of "string"

Have to import "using System"

33. Enums

What is?

A set of name/value pairs (constants)

When to use?

you've a number of related constants

Eg.

public enum ShippingMethod{ RegularAirMail = 1, RegisteredAirMail = 2, Express = 3;}

Info

Internally an Integer

How to change to byte?

public enum ShippingMethod : byte{ RegularAirMail = 1, RegisteredAirMail = 2, Express = 3;}

How to use?

Eg.

var method = ShippingMethod.Express;

How to use?

Convert to Int

Cast

Eg.

Console.WriteLine((int)method);

return

Convert to String

.ToString() method

Eg.

var methodStr = ShippingMethod.RegisterdAirMail.ToString();Console.WriteLine(methodStr);

Convert to Enum

Parse

Eg.

var methodName = "RegisterdAirMail";var shippingMethod = (ShippingMethod)Enum.Parse(typeof(ShippingMethod), methodName);

return

"RegisterAirMail"

34. Demo - Enums

35. Reference Types & Values Types

Primitive Types

Eg.

int

char

float

bool

Non-primitive Types

Eg.

classes

structures

arrays

map to

System.Array

strings

map to

System.String

2 main types

for which we create new types

What are they?

Value Types

Structures

for

Primitive types

Custom structures

Allocate on stack

Memory allocation done automatically

Immediately removed when out of scope

by Runtime/CLR

Reference Types

Classes

for

Arrays

Strings

Custom classes

Need to allocate memory

using "new"

Memory allocated on

Heap

more sustainable

if object goes out of scope, it won't be removed immediately. It'll continue to be in heap for a little while.

Garbage collected by Runtime/CLR

Copying of reference types & value types are different